Cables for communicating electrical signals in entertainment systems for vehicles normally must meet requirements pertaining to electromagnetic interference (EMI). The requirements for EMI suppression are generally the most stringent for cables used on aircraft. There are two areas of the electromagnetic spectrum in aircraft that tend to be problematic. The first is the very high frequency range (VHF), reserved for pilot communication. The second is the frequency range reserved for the global positioning system (GPS). However, it is important to prevent EMI in other areas as well due to the potential for great loss of human life in aviation related accidents.
Cable manufacturers in the past have provided EMI suppression by including a sheath of internal copper braid or other metal or alloy disposed under an outer sheath of a polymeric material. While the braid suppresses EMI, it has disadvantages. One disadvantage is increased weight, an important factor in the aviation field, especially for commercial air transport where profit margins are typically low. In this regard, entertainment system cabling for commercial passenger aircraft can add significant weight to the vehicle.
Another disadvantage is that the braid increases the diameter of the cable and decreases flexibility. The increase size and decreased flexibility makes it more difficult to route the cable. Decreased flexibility is especially problematic because the cable is frequently used to connect to components of an entertainment system that require flexibility, such as a personal control unit, handset or game controller that passengers need to manipulate. Decreased flexibility makes it more difficult for passengers to manipulate the component and/or position it at a comfortable location.
In addition, the metal comprising the braid is subject to bending, which results in fatigue and eventually breaks. The breakage results in small, sharp pieces of metal becoming embedded in the cable outer sheath, which has resulted in injuries to persons handling the cable, such as aircraft passengers.
In the past, pieces of metal have also penetrated inward into the cable and caused shorts between wires in the cable. In particular, the metal pieces penetrate into the insulation surrounding wires in the cable and short one wire to another. The problem has become more acute with the introduction of USB connections through the cables. With USB, the cables carry more power and therefore short circuiting is more serious. There have been incidents causing smoke and/or fire. Smoke and fire is an incident reportable to the Federal Aviation Authority (FAA) and can force an aircraft to turnaround or land at the nearest airport, causing delay, inconvenience and increased costs to the airline and/or passengers.
Disclosed herein is a cable, a cable assembly, and method or process for making a cable and cable assembly that addresses the foregoing problems.